drivers/clk/mxs/clk-frac.c

Source file repositories/reference/linux-study-clean/drivers/clk/mxs/clk-frac.c

File Facts

System
Linux kernel
Corpus path
drivers/clk/mxs/clk-frac.c
Extension
.c
Size
2998 bytes
Lines
141
Domain
Driver Families
Bucket
drivers/clk
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct clk_frac {
	struct clk_hw hw;
	void __iomem *reg;
	u8 shift;
	u8 width;
	u8 busy;
};

#define to_clk_frac(_hw) container_of(_hw, struct clk_frac, hw)

static unsigned long clk_frac_recalc_rate(struct clk_hw *hw,
					  unsigned long parent_rate)
{
	struct clk_frac *frac = to_clk_frac(hw);
	u32 div;
	u64 tmp_rate;

	div = readl_relaxed(frac->reg) >> frac->shift;
	div &= (1 << frac->width) - 1;

	tmp_rate = (u64)parent_rate * div;
	return tmp_rate >> frac->width;
}

static int clk_frac_determine_rate(struct clk_hw *hw,
				   struct clk_rate_request *req)
{
	struct clk_frac *frac = to_clk_frac(hw);
	unsigned long parent_rate = req->best_parent_rate;
	u32 div;
	u64 tmp, tmp_rate, result;

	if (req->rate > parent_rate)
		return -EINVAL;

	tmp = req->rate;
	tmp <<= frac->width;
	do_div(tmp, parent_rate);
	div = tmp;

	if (!div)
		return -EINVAL;

	tmp_rate = (u64)parent_rate * div;
	result = tmp_rate >> frac->width;
	if ((result << frac->width) < tmp_rate)
		result += 1;
	req->rate = result;

	return 0;
}

static int clk_frac_set_rate(struct clk_hw *hw, unsigned long rate,
			     unsigned long parent_rate)
{
	struct clk_frac *frac = to_clk_frac(hw);
	unsigned long flags;
	u32 div, val;
	u64 tmp;

	if (rate > parent_rate)
		return -EINVAL;

	tmp = rate;
	tmp <<= frac->width;
	do_div(tmp, parent_rate);
	div = tmp;

	if (!div)
		return -EINVAL;

	spin_lock_irqsave(&mxs_lock, flags);

	val = readl_relaxed(frac->reg);
	val &= ~(((1 << frac->width) - 1) << frac->shift);
	val |= div << frac->shift;
	writel_relaxed(val, frac->reg);

	spin_unlock_irqrestore(&mxs_lock, flags);

	return mxs_clk_wait(frac->reg, frac->busy);
}

static const struct clk_ops clk_frac_ops = {
	.recalc_rate = clk_frac_recalc_rate,
	.determine_rate = clk_frac_determine_rate,
	.set_rate = clk_frac_set_rate,
};

struct clk *mxs_clk_frac(const char *name, const char *parent_name,

Annotation

Implementation Notes